1. Technical Field
The present invention relates an apparatus for manufacturing molten iron using powder ore in a smelting reduction process. The apparatus restrains a phenomenon in which the powder ore is piled up between a lower portion and an inner wall of the fluidized-bed reduction reactor to form stagnating layers, disturb gas flow, and deteriorate reaction efficiency.
2. Background Art
The iron and steel industry is a core industry that supplies the basic materials needed in construction and in the manufacture of automobiles, ships, home appliances, and many of the other products we use. It is also an industry with one of the longest histories that has progressed together with humanity. In an iron foundry, which plays a pivotal role in the iron and steel industry, after molten iron, which is pig iron in a molten state, is produced by using iron ore and coal as raw materials, steel is produced from the molten iron and then supplied to customers.
At present, approximately 60% of the world's iron production is realized by using the blast furnace process developed from the 14th century. In the blast furnace process, coke produced by using bituminous coal and iron ore that have undergone a sintering process are charged into a blast furnace, and hot gas is supplied to the blast furnace to reduce the iron ore to iron, to thereby manufacture molten iron.
The blast furnace method, which is the most popular in plants for manufacturing molten iron, requires that raw materials have strength of at least a predetermined level and have grain sizes that can ensure permeability in the furnace, taking into account reaction characteristics. For that reason, coke that is obtained by processing specific raw coals is needed as a carbon source to be used as a fuel and as a reducing agent. Also, sintered ore that have gone through a successive agglomerating process is needed as an iron source.
Accordingly, the modern blast furnace method requires raw material preliminary processing equipment, such as coke manufacturing equipment and sintering equipment. Namely, it is necessary to be equipped with subsidiary facilities in addition to the blast furnace, and also equipment for preventing and minimizing pollution generated by the subsidiary facilities. Therefore, a heavy investment in the additional facilities and equipment leads to increased manufacturing costs.
In order to solve the above problems of the blast furnace process, a smelting reduction process has been developed and researched by many countries. In the smelting reduction process, molten iron is manufactured in a melter-gasifier by directly using raw coal as a fuel and a reducing agent, and powder ore that makes up 80% or more of the world ore production as an iron source.
In the smelting reduction process, a two step reducing method composed of preliminary reducing and final reducing is considered to be mainstream. The conventional apparatus for manufacturing molten iron consists of a fluidized-bed reduction reactor in which bubble fluidized beds are formed and a melter-gasifier connected to the fluidized-bed reduction reactor, in which coal packed beds are formed. The powder ore and the additives at room temperature are charged into the fluidized-bed reduction reactor and pre-reduced.
Since hot reducing gas is supplied to the fluidized-bed reactors, the temperature of the iron ore and additives is raised by contacting with the hot reducing gas. Simultaneously, 90% or more of the iron ore and additives are reduced and 30% or more of them are plasticized, and they are charged into the melter-gasifier.
Meanwhile, in the fluidizing reduction process, the powder ore charged into the fluidized-bed reduction reactor goes through a process of rising and reducing in height by the reducing gas supplied from the melter-gasifier. The powder ore rises to a certain height depending on its properties such as particle size, density, and so on. Then, the powder ore generally drops again along an inner wall of the fluidized-bed reduction reactor where few gas streams exist.
However, when the gas flow of the reactor is not smoothly formed due to various reasons such as a sudden change of the gas stream during the operation, the dropped powder ore may not rise again and it may pile up between a lower portion and an inner wall of the fluidized-bed reduction reactor to form a layer.
As described above, the layer formed between the lower portion and the inner wall of the fluidized-bed reduction reactor is called a stagnating layer. In particular, when the operation instability lasts or an impact by the fluctuation of the gas stream is too great, the powder ore forming the stagnating layers will not rise again. Thus, the stagnating layers disturb the flow of the powder ore and the gas in the fluidized-bed reduction reactor.
As described above, the abnormal flow of the powder ore and the gas caused by the stagnating layers allows the stagnating layers to grow more. It also causes a vicious circle in which the flow of the powder ore and the gas is further disturbed. Thus, the normal function of the fluidized-bed reduction reactor is seriously deteriorated.
The present invention is for providing an apparatus for manufacturing molten iron that can restrain abnormal formation of stagnating layers of powder ore in a smelting reduction process.